Intrinsically photosensitive retinal ganglion cells

Jul 3, 2010Science China. Life sciences

Light-sensitive cells in the eye that detect brightness

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Circadian Biology on OpenScience ↗PubMed ↗DOI ↗

Abstract

A new mammalian photoreceptor has been identified in the ganglion cell layer of the inner retina.

These intrinsically photosensitive retinal ganglion cells (ipRGCs) contain melanopsin, allowing them to detect light without input from traditional rod and cone photoreceptors.
IpRGCs extend their dendrites broadly across the retina, making them effective at assessing ambient light changes.
The process of light detection in ipRGCs is mediated by channels that are more similar to those found in invertebrates than in vertebrates.
IpRGCs transmit light information through the optic nerve to the hypothalamic suprachiasmatic nucleus (SCN), influencing circadian rhythms.
These cells play a role in regulating pupil size and may interface with the autonomic nervous system to influence gene activity in major organs.
IpRGCs also provide excitatory input to dopaminergic amacrine cells, potentially leading to new insights into retinal circuit modifications by light.

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A new mammalian photoreceptor was recently discovered to reside in the ganglion cell layer of the inner retina. These intrinsically photosensitive retinal ganglion cells (ipRGCs) express a photopigment, melanopsin that confers upon them the ability to respond to light in the absence of all rod and cone photoreceptor input. Although relatively few in number, ipRGCs extend their dendrites across large expanses of the retina making them ideally suited to function as irradiance detectors to assess changes in ambient light levels. Phototransduction in ipRGCs appears to be mediated by transient receptor potential channels more closely resembling the phototransduction cascade of invertebrate than vertebrate photoreceptors. ipRGCs convey irradiance information centrally via the optic nerve to influence several functions. ipRGCs are the primary retinal input to the hypothalamic suprachiasmatic nucleus (SCN), a circadian oscillator and biological clock, and this input entrains the SCN to the day/night cycle. ipRGCs contribute irradiance signals that regulate pupil size and they also provide signals that interface with the autonomic nervous system to regulate rhythmic gene activity in major organs of the body. ipRGCs also provide excitatory drive to dopaminergic amacrine cells in the retina, providing a novel basis for the restructuring of retinal circuits by light. Here we review the ground-breaking discoveries, current progress and directions for future investigation.

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Intrinsically photosensitive retinal ganglion cells

Abstract

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